CAIRO (AFP) - Egypt's interior ministry on Saturday issued a new warning to Islamist protesters, pledging to crack down if demonstrators block roads or obstruct traffic.

The ministry statement came a day after thousands of protesters rallied in Cairo against the military's July 3 overthrow of Islamist president Mohamed Mursi.

It accused the protesters of committing "many crimes" such as blocking traffic and "kidnapping journalists and confiscating their equipment".

"The ministry affirms that it will confront with utmost decisiveness practices such as blocking roads or obstructing traffic or threatening the security of citizens," the statement said.

Hundreds of people have been killed and more than 2,000 arrested in a police crackdown on Mursi's Muslim Brotherhood movement since Aug 14, when police forcibly dispersed two protest camps.

The Islamists have continued to call weekly rallies, insisting that they are committed to peaceful protest.

On Saturday, roughly 200 protesters in Cairo marched near the Rabaa al-Adawiya square which was the site of the main protest camp dispersed a month ago.

Hundreds were killed in the operation to clear the camp and another Cairo sit-in, in what Human Rights Watch described as "most serious incident of mass unlawful killings in modern Egyptian history".

The government defended the operation, saying it was measured and that police acted with self-restraint after coming under fire from protesters.